Current trap mufflers (e.g., U.S. Pat. No. 4,851,015) provide for trap regeneration and, during regeneration, have an external bypass which exhausts through an alternative muffler to atmosphere or through an alternative trap muffler system to atmosphere. The problem is that trap filters become clogged and must be periodically regenerated by burning or oxidizing the particulates captured therein. For regeneration systems having electrical heaters, there is insufficient vehicle electrical energy to create sufficient continuing heat to maintain regeneration if exhaust continues to flow through the trap during regeneration without major additions to the electrical system. (Some systems, e.g., burners, are capable of providing sufficient heat without bypass.) In addition, current systems bypass into additional devices. Thus, current systems, although effective in a laboratory setting, are very bulky and somewhat complex when installed to provide a complete vehicle capability. Reduction in size and complexity results in less cost, weight, etc., and is clearly desirable. The present invention addresses this problem.
Additionally, regeneration of current trap filters proceeds in a forward direction from upstream nearest the engine to downstream nearest atmosphere. The filters load more greatly at the downstream end. As a flame front during regeneration proceeds, on many systems it may not completely oxidize particulate build-up at the downstream end and, over time, the filter may become clogged or on a, following regeneration, burn with extreme temperatures to the point of damaging the filter. The present invention provides an advantageous concept for internal bypass which furthermore allows reverse regeneration starting at the downstream end where the greater particulate build-up exists and proceeding toward the upstream end.
Many other features of the invention which address these and other problems with current systems will become apparent hereinafter.